action. We all know cochlear implants can change the lives of children who believe they will then learn like other kids do. 90% of insurance companies cover the cost. But what if you were a family that didn't notice a line in your policy and your child has to pay the price? Abc's dan harris with our investigation and a wake-up call for anyone buying insurance. Reporter: You have to look closely but if you keep your eye on the boy in the orange shirt, his name is carson. You'll see he is consistently one step behind his preschool classmates. Math friend. Carson. Reporter: Staring off when the teacher's talking to him. Reporter: Still sitting for a few seconds. Go find a card and count out. Reporter: When all the other children stand up -- I think he's constantly trying to keep up with everybody else. Reporter: Carson rubin, who's five, has a condition called "auditory neuropathy," which means that while the teacher sounds like this to the rest of the children -- car rots and onions? Healthy or unhealthy? Reporter: To carson, she sounds like this. Have you -- um -- ever been to the dentist? I can't hear you. Reporter: Cochlear implants could dramatically improve carson's hearing. Which could have miraculous impacts. Just watch as this child's device are turned on for the first time. Can you hear it? . But it would cost a quarter of a million dollars and the rubins' health insurance company wouldn't cover it. When they came back to you and they said, "we're not going to cover this," what was your reaction? I was shocked. Welcome to coventry healthcare. Reporter: The rubins are covered by coventry healthcare of georgia. We looked at the rubins' policy and right there, on page 33, at the bottom of a long list of exclusi exclusions, there it is, hearing devices and implants. Experts say companies have wide latitude to create exclusions like this, so you have to check your policy closely. We made repeated requests for an interview but coventry would only tell us -- quote, "no health insurance policy covers every procedure." In 2011 alone, coventry made half a billion dollars in profit. This is their ceo, alan wise, number 53 on the forbes list of richest executives. What would you say to him? Sir, if you were in our same pokz and you were told, repeatedly, no, no, no, how would you feel? If our salaries were swapped, how would you feel? Reporter: After the interview, we made one last call to the company. This time they thanked us for bringing it to their attention and said they will now cover cochlear implants in georgia, including for carson. To have the insurance company call and you say, okay, we're going to cover this, that must have been huge. I couldn't breathe for a while. Reporter: Carson will have surgery in weeks. His mother says he's very excited. Bear this in mind. Every yearore than a thousand children who need cochlear implants are denied in america. And even though coventry changing its policy in georgia, in 23 other states in which the company operates, the exclusion will remain in place.

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